1. Technical Field
The present invention relates to a data transmitting and receiving system performing transmission and reception of data between terminals connected to a network via a relay device.
2. Background Art
There have been proposed techniques to realize packet communications reducing delay in an environment of a network (typically referred to as an ad-hoc network, or a mesh-type network) which entirely consists of wirelessly connectable terminals (personal computer), the Personal Digital Assistant (PDA), cellular phone, and car navigation system), and dispenses with an access point such as a wireless Local Area Network (LAN). One of such techniques, for example, is a route switching technique which sets routes between transmitting and receiving terminals and periodically provides a control packet to each of the routes in order to measure an end-to-end delay, select one of the routes always having the least delay, and transmit a packet.
This ad-hoc network, however, has a long transmission delay problem. Besides, the ad-hoc network suffers another problem of data loses caused by the buffer overflow at a relay device interconnecting the terminals and the resulting congestion, and by occurrence of a transmission error since interconnections are established between relaying devices, and a relay device and a transmitting and receiving terminals.
Hence, occurrence of the data losses caused by the congestion and the transmission error leads to problems of video and audio data quality degradation including a distorted image and skipping sound when transmitting the video and the audio data.
Specifically, determination is to be made in that which cause, the congestion or the transmission error both developing the data losses when conducting wireless transmission, influences the data loss to what degree.
In order to overcome the problems, a possible technique is to apply i) a technique (Patent Reference 2) for setting a transmission rate and intensity of an error correction code, distinguishing between the transmission error and the congestion, by periodically transmitting an observation packet to ii) a technique (Patent Reference 1) for correctly measuring a traffic amount at the routing device by the periodical transmission of an observation packet for observing transmission quality between the transmitting and receiving terminals in the ad-hoc network.    Patent Reference 1: Japanese Unexamined Patent Application Publication No. 2005-347879    Patent Reference 2: Japanese Unexamined Patent Application Publication No. 2003-152752